This invention relates to shaft couplers and in particular to a self-tightening shaft coupler for conveniently, reliably, and safely joining a pair of axially aligned rotatable shafts.
The need to couple two axially aligned rotatable shafts arises frequently in a variety of diverse applications. For example, it is a common and well known practice to obtain operating power for operating various auxiliary agricultural devices, such as sprayers, spreaders and reapers, by coupling a drive shaft on the auxiliary device to the splined power take-off shaft of an agricultural tractor. To facilitate joining the shafts, a variety of shaft couplers have been developed which, in addition to providing an effective coupling, seek to provide reliability, safety and convenience as well.
One well known prior shaft coupler consisted of a generally cylindrical sleeve having an interior bore for receiving both the power take-off, and auxiliary device, shafts. A series of cam-actuated pins, encircling the sleeve, projected into a circumferential groove formed on the splined power take-off shaft to prevent relative axial movement between the coupler and the shaft. In order to help secure the coupler to the auxiliary device drive shaft, a set-screw was provided in the coupler and was arranged to engage, and bear against, the auxiliary drive shaft.
While this prior shaft coupler was effective when properly installed, the set-screw was subject to inadvertent loosening resulting in slippage of the coupler, scoring of the auxiliary device drive shaft, and potentially hazardous wobbling between the auxiliary device and the supporting power take-off shaft. Even when tight, the set-screw, in bearing against the auxiliary device shaft, unavoidably forced the shaft into slight axial misalignment with the coupler, which, in itself, was a source of vibration in the auxiliary unit. Such vibration contributed to reduced bearing life in the auxiliary unit and tended to promote loosening of the set-screw.
In addition to the foregoing, the set-screw of such prior shaft couplers often protruded from the exterior of the coupler and formed a potential hazard as the coupler rotated conjointly with the shafts. The mechanism for operating the cam-actuated locking pins may pose a similar hazard.
The present invention is directed to an improved shaft coupler which is convenient to use, reliable and safe in operation, and which avoids the drawbacks of prior couplers. The coupler includes a pair of externally threaded, compressable collets, at opposite ends of a rigid coupler member. The threads are formed such that rotation of the power take-off shaft tends to tighten the collets with the effect that self-tightening operation is obtained. Since the collets constrict evenly around the shafts they engage, no misalignment between the shafts results as the coupler tightens.
In one principal aspect of the present invention, a coupler for joining a pair of shafts in generally axial alignment includes a elongate coupler member and collet at one end of the member in threaded engagement therewith. The collet is provided with an interior recess for receiving and engaging one of the shafts in order to join the coupling member thereto. Means are provided at the other end of the coupling member to engage the remaining shaft and thereby join the coupling member thereto.
In another principal aspect of the present invention, the collet is rotatably received in the elongate coupler member such that the rotational position of the collet relative to the member determines the dimension of the interior recess formed therein. Thus, the collet constricts onto the shaft as the collet rotates relative to the coupling member.
In still another principal aspect of the present invention, an additional collet, for engaging the remaining one of the shafts, is provided at the other end of the coupling member.
In still another principal aspect of the present invention, the threading of the collets at each end of the coupling member is such that rotation of the shafts in a predetermined direction tends to tighten each of the collets onto the shaft it engages.
In still another principal aspect of the present invention, one of the collets includes axially extending grooves for receiving the splines of a splined shaft therein.
In still another principal aspect of the present invention, one of the collets includes an axially extending groove for receiving a key contained in a keyway formed in one of the shafts.
In still another principal aspect of the present invention, the elongate coupling member is a generally cylindrical hollow sleeve.
In still another principal aspect of the present invention, each of the collets is of a hexagonal cross-section over a portion of its exterior to facilitate tightening and loosening with a wrench.
In still another principal aspect of the present invention, at least one of the collets is provided with a tapered exterior surface for engaging the interior of the coupling member upon axial movement therein such that the dimension of the interior of the collet decreases upon movement of the collet into the coupling member.
In still another principal aspect of the present invention, at least one of the collets is provided with two of such tapered exterior surfaces.
These and other objects, features and advantages of the present invention will be clearly understood through consideration of the following detailed description.